The fracture strength of constant velocity universal joints in the case of which torque is transmitted by balls guided in windows of the cage is substantially determined by the fracture strength of the cage. Between the individual windows accommodating the balls there are provided webs which, for design and geometric reasons, cannot be reinforced by just any amount.
It is the object of the present invention to provide a cage for a constant velocity universal joint in the case of which the fracture strength of the cage is increased without restricting the freedom of movement of the joint.
In accordance with the invention, the objective is achieved in that the circumferentially extending contact faces for the balls at the windows are aligned in such a way that, at least in the center plane of the cage, their radial extensions are tangent or contact a sphere virtually arranged at the point of intersection between the radial center plane of the cage and the joint axis, and that the diameter of the sphere approximately corresponds to the diameter of the balls held in the cage.
The advantage of the cage embodiment in accordance with the present invention is that the strength of the individual webs of the cage is substantially increased by increasing the cross-section of the web. This is of particular significance in that it is the webs which determine the fracture strength of the cage when subjected to loads.
According to a method of producing the cage in accordance with the present invention it is proposed that during a first punching operation, a machining allowance is taken into account, that finish-machining is undertaken by a tool which is pivotable around the longitudinal axis of the cage and that the finish-machining operation is followed by a surface treatment or hardening operation.
The advantage of the method described is that the cage production costs are not increased.
In this case, the finish-machining operation used in conventional production processes is replaced by a milling or grinding operation.
The surface treatment following the finish-machining operation does not have to be followed by any further machining operations.
According to a further embodiment of the present invention, it is proposed that while the tool is stationary, but rotating, the cage is subjected to a pivot movement around its longitudinal axis.
This operation may be carried out by a pivoting device for the cage.
According to an advantageous characteristic of a method for producing a cage for a constant velocity universal joint, the surface treatment of the cage takes place prior to finish-machining the cage.
If grinding constitutes the finish-machining operation, there will be no problems when the surface treatment takes place in advance of the finish-machining operation. But nowadays it is also possible to provide the surface-treated cage with the required shape by carrying out a milling operation.